The present invention relates generally to the field of security access systems and, more particularly, to a computerized cost effective entry control system which provides high levels of security, convenience and flexibility.
Individual push-button operated locks have been used to secure doors of dwellings as well as vehicles. Such locks are described in U.S. Pat. Nos. 3,953,769; 4,149,212; and 4,477,806, each of which discloses a stand-alone push-button lock programmed at the location of the lock to respond to an access code.
The only push-button system known to the present inventor for securing a large number of access locations was manufactured by Tool Research Engineering of Santa Ana, Calif., under the name "Digikey". The Digikey system has a keypad at access locations with no local storage or processing capabilities. The keypads are connected together as an operating unit by a large number of wires leading to a central control computer.
In the Digikey system, a four-digit number entered on a keypad at the access location is transmitted to the central computer which determines whether the number is a valid access code. If the number is valid, a signal from the computer unlocks the door. In a hotel installation, the valid access code is chosen by a guest when he checks in. To do so, he enters a four-digit number on a keypad at the front desk. The number is then stored in the central computer at the front desk for subsequent use in opening the door. As far as applicant is aware, there is no provision in the Digikey system for deviating from a four-digit entry code, and only one code can be stored for each room.
Other systems for controlling accesses in large building complexes involve the use of machinereadable "card keys" which may or may not resemble mechanical keys. Such devices are described in U.S. Pat. Nos. 3,622,991; 3,694,810; 4,157,534 and 4,415,893. The use of physical keys of any type involves some disadvantages. While some of the physical key systems disclosed in the patents above have storage and comparison capabilities at each controlled access, many are cumbersome in their implementation. For example, the devices of U.S. Pat. Nos. 3,622,991 and 4,157,534 require extensive hardwire networks or microwave transmission devices for communication. U.S. Pat. No. 4,415,893 is somewhat distinct in stressing the desirability of retaining the mechanical parts of a conventional door lock, with the pin tumbler replaced by an electronic reading cylinder of identical size. This is proposed for the purpose of maintaining the "feel" of a mechanical lock. The patent clearly teaches away from the development of a keyless system.
To some extent, keyless systems isolate the locking mechanism from direct manipulation by an unauthorized person; however, other problems arise. Specifically, the problems of electronic meddling or tampering at various levels are introduced. In that regard, with the widespread use of portable computers, it may be a relatively simple matter for an unauthorized person to couple a computer to an electronic access control system. That likelihood becomes a particularly significant problem with regard to a data-bus system as contemplated by the present invention. Accordingly, a considerable need exists for an economical access control system that is expedient to install, effective in operation and relatively safe with regard to the host of possible techniques for an improper entry. The need is complicated in installations as hotels where access by service and cleaning people must be accommodated and halls are freely accessible to all persons. Additionally, persons authorized to enter rooms change daily and must be accommodated rapidly during a brief contact as at the front desk of a hotel.